This disclosure relates to new antistatic additives, polymer compositions comprising these additives, as well as methods of making these additives and polymer compositions.
Antistatic agents constitute a unique class of polymer additives. They prevent an accumulation of static electricity on the surface of an article fabricated of the polymer. They also offer aesthetic values by preventing the accumulation of surface dust on the article. For example, lenses of automotive headlamps are typically made of polymers, such as polycarbonates, which have a desirable combination of heat stability, dimensional stability, transparency, and ductility. In the past, the optics system (also sometimes called “Fresnel”) necessary to properly focus the headlight beam on the road did not have a smooth profile. Consequently, the dust that accumulated on the lens surface, either during fabrication, or during the service life of the headlamp, was not conspicuously visible. But as the automotive industry moves towards lenses with a smoother profile, the accumulated dust becomes more easily visible, therefore leading to aesthetics issues.
Similarly mitigation of static charge buildup is important in conveyor belt design. Conveyor belts are typically made mostly of synthetic polymeric materials. Use of plastic in conveyor belts has led to several distinct advantages in conveyor belt technology, such as cleanliness, reliability, decreased noise, low cost to lifetime ratio, modularity, and flexibility. As a result of these advantages, plastics-based conveyor systems are being used in hyper clean (class 100 or higher) environments essential for the manufacture of advanced electronics products and systems. But as product dimensions and tolerances approach sub-micron levels, electrostatic discharge, a phenomenon inherent of plastic materials, poses increasing problems to the high technology manufacturers that use plastic conveyor components. The buildup of surface charge results in secondary dirt contamination, which has undesirable consequences, especially for precision, high technology electronic components.
Antistatic agents may be applied in two ways: externally and internally. External antistatic agents are applied by spraying the surface, or dipping the polymeric material in a medium containing the antistatic agent. Internal antistatic agents are added to the polymer before processing. For this reason, internal antistatic agents have to be thermally stable and preferably migrate to the surface during processing. Additionally, the incorporation of the antistatic agent should not diminish desirable characteristics of the polymeric material such a transparency and glass transition temperature (Tg). Several types of antistatic agents are available, but agents with improved properties, such as processability, thermal stability and/or resin compatibility are needed.
It is therefore desirable to identify more effective antistatic agents as additives that can be incorporated into polymers without adversely affecting the physical and chemical properties of the resulting polymer compositions.